In situ microstructure and rheological behavior of yeast biofilms from the juice processing industries

Abstract

The factors affecting the mechanical properties of biofilms formed by yeast species (Rhodotorula mucilaginosa, Candida krusei, C. kefyr and C. tropicalis) isolated from the juice processing industries have been investigated. Variables studied were: the food matrix (apple/pear juice), the sugar concentration (6/12 °Bx) and the hydrodynamic conditions (static/turbulent flow). A range of environmental cues were included as the mechanical properties of biofilms are complex. Yeast counts were significantly higher in turbulent flow compared with under static conditions. The thickness of the biofilm ranged from 38 to 148 μm, from static to turbulent flow. Yeast biofilms grown under turbulent flow conditions were viscoelastic with a predominant solid-like behavior and were structurally stronger than those grown under static conditions, indicating gel-type structures. Only the type of flow had a significant effect on [Formula: see text] and G*. Flow velocity and nutrient status modulated the biofilm thickness, the biomass and the mechanical properties. A better knowledge of the factors controlling biofilm formation will help in the development of control strategies.

Overview on the hydrodynamic conditions found in industrial systems and its impact in (bio)fouling formation

“…changed its shape and increased the production of extracellular polymeric substances to ensure robust cell adhesion. Also, the viscoelastic properties of biofouling were adjusted to shear stress conditions, becoming cohesive and solid-like under turbulent conditions [203,204]. Thus, it is obvious that biofouling formed under high shear stress is more difficult to eradicate by mechanical and chemical processes, affecting surface cleaning and disinfection efficiency, as demonstrated for P. fluorescens and B. cereus biofilms by Simões et al [22,205,206].…”

Biopelículas y persistencia microbiana en la industria alimentaria

“…Sin embargo, cada vez es más evidente que existe una micro-heterogeneidad dentro de las biopelículas (Liu et al, 2015;Gingichashvili et al, 2017; Tack, Nimmegeers, Akkermans, Hashem y van Impe, 2017), con la existencia de fenómenos de diferenciación metabólica entre las distintas células que las constituyen. También se sabe que varios factores relacionados con los alimentos, como la concentración de nutrientes, la disponibilidad de oxígeno, la composición de la matriz alimentaria, la concentración de azúcar y las condiciones hidrodinámicas, pueden influir en la arquitectura de la biopelícula (Cherifi, Jacques, Quessy y Fravalo, 2017;Tarifa, Genovese, Lozano y Brugnoni, 2018;Turonova et al, 2015).…”

The mechanical properties of microbial surfaces and biofilms

“…The mechanical properties of biofilms from Rhodotorula mucilaginosa , Candida krusei , Candida kefyr and Candida tropicalis were examined with a focus on industrial applications. Essentially, yeast biofilms of these species were determined to be viscoelastic materials with a solid-like behavior ( Brugnoni et al, 2014 , Tarifa et al, 2017 ).…”